Expression node bit shift

Is this a bug or am I just thinking about this wrong? The attached VI shows a U8 going through an expression node where the expression is "x << y". I've tried multiple versions of y and as soon as y becomes large enough to shift all the original 1's off the U8, the result becomes 0xFF instead of 0x00. I would assume that its intent was to match C's functionality since it matches C's syntax but this does not appear to be the case.
Any suggestions or is this a bug?
Thanks
Andy Brown
Averna
Attachments:
expression_shift_issue.vi ‏11 KB

Hey Andy,
Thank you for contacting National Instruments. It does look like that is acting strangely. However, we do have a Logical Shift VI that I believe accomplishes what you are looking for.
On the Block Diagram, go to Programming>>Numeric>>Data Manipulation>>Logical Shift.
It takes two inputs, x and y, with x being the original number, and y being the number of bits you want to shift. It looks like it will clear out to 00 once all the bits have been shifted over.
Let me know if you any questions!
Regards,
Kevin H
National Instruments
WSN/Wireless DAQ Product Support Engineer

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Hi Catherine,
I've tried your suggestion earlier and tried it again after your
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Error on line 1 is marked by a '#' character: "~#"
[Image]
Pat S.
cfpautx wrote:
> Hello Pat,
> The way to fix this problem is fairly simple, if you change your
> inputs and outputs to I8, u16 or I16 it will run correctly.
> Regards,
> Catherine Petronino
> National Instrument
> www.ni.com/ask

Problems with bit shift left in Formula Node

Hi,
Sorry but my English is not good.
I'm trying to execute a bit shift left in the Formula Node, but the shift left is not working as I expected.
uInt32 parametro[5];
float32 valorAmostra;
int16 indiceAmostra;
uInt8 indiceResposta;
int16 controle;
int32 valor;
int8 i;
for(i=0; i<5; i++)
parametro[i]=param[i];
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indiceResposta = (controle >> 10);
valorAmostra = valor & 0x7FFFFF;
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if((valor & 0x800000) == 0x800000)
valorAmostra = valorAmostra*(-1);
the input param array is of the type uInt8, as I saw in other topics that does not shift with uInt8,
I copy the values of param array to parametro which is of type uInt32, but still did not work.
Testing the input param with the following values:
param[] = {10,14,10,0,16}
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Solved!
Go to Solution.

Portuguese:
Olá,
Existe um bug no LabVIEW para esta operação. Este bug deverá ser corrigido em versões futuras. Uma solução para esta situação é utilizar um int32 ao invés de um ulnt32.
Qualquer dúvida por favor entre em contato.
Obrigado.
English:
I investigated the problem you are having, and it turns out that it is a bug that has already been reported and documented. The work around for it is to use int32 rather than uInt32.
Thanks.
Luciano Borges
R&D Engineer
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Darin.K wrote:
That is easily in my top 2 or 3 LV pet peeves. I use exponentiation countless times and the next time I use bit-wise XOR in a LV text formula will be my first. Why couldn't LV be like every other program/language I have used and use ^ for exponentiation?
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Hi everyone!
I have a question about bit shifting. When I attempt to shift 32 bit on a int value, the output is the same value. It doesn't matter if I try to make a rigth or left shifting. It also hapend when I make 64 bit shifting on a long value. I supposed it should be 0. This is the code I'm woking with:
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Could someone help me to understand why this happend?
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GerSua wrote:
Hi everyone!
I have a question about bit shifting. When I attempt to shift 32 bit on a int value, the output is the same value. It doesn't matter if I try to make a rigth or left shifting. It also hapend when I make 64 bit shifting on a long value. I supposed it should be 0. This is the code I'm woking with:
int x = 2147483647;
System.out.println("Output1 = " + (x >> 32));
System.out.println("Output2 = " + (x << 32));
Output:
Output1 = 2147483647
Output2 = 2147483647
Could someone help me to understand why this happend?
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Attachments:
typedef does not connect to expression node.vi ‏7 KB
dbl typedef.ctl ‏5 KB

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mtf wrote:
Are there any libraries or reccomended techniques foir large-scale bit-shifting.
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Expression node bit shift

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